Shelf Sea Biogeochemistry blog

Saturday, 29 November 2014

Glorious mud

Ocean research cruise blog of Jonathan Sharples

We reached the northern-most station by about 7 pm last night. There
was great excitement watching the data from the CTD as it was lowered
through the water. If any site was going to have reached the fully mixed
winter state by now, it was going to be this one. About a dozen of the
scientists were crowded around the CTD computer in the main lab, willing
the temperature of the water to stay the same as the CTD went lower.
But there was a collective groan as a thermocline appeared at 66 metres
below the surface. It’s a bit disappointing that we are not going to be
out here to see that final transition to the winter mixed water, but I’m
pleased that I appear to have generated so much enthusiasm for shelf
sea physics amongst the crowd of biogeochemists on board.

box corer

Matthew Bone, from the University of East Anglia, is interested in
the muddy seabed at this site. We collected 4 cores from the seabed
using a large “box corer”. This is a large steel cylinder that is
lowered down onto the seabed, and then pushed into the seabed by the
large weights above it. When it is pulled out, a core of the seabed mud
is held within the cylinder and brought on board. Matt has been working
on measuring how the mud releases nutrients back into the water. This
muddy area of seabed, in an area called the Celtic Deep, is an important
fishing ground for a scampi that lives on, and burrows into, the mud.
At one point last night the radar was showing 12 fishing vessels around
us, within a distance of about 10 miles. One of the cores caught a
scampi. It seems happy enough in the lab, busily shifting mud around the
top of the core and tending a burrow. The plan is to release it later
today when we pass over another area where we have in the past seen
scampi on the seabed.